Melt-spinning system



July 25, 1961 w. v. HENRY 2,993,230

MELT-SPINNING SYSTEM Filed May 5, 1958 2 Sheets-Sheet l INVENTOR.

WILLIAM v. HENRY F1. g- 1 BY m; (J. ATiOR qEY July 25, 1961 w. v. HENRY 2,993,230

MELT-SPINNING SYSTEM Filed May 5, 1958 2 Sheets-Sheet 2 INVENTOR. WILLIAM V. HENRY ATT RN Y solution.

United States Patent 2,993,230 MELT-SPINNING SYSTEM William V. Henry, Asheville, N.C., assignor to American Erika Corporation, Enka, NC, a corporation of Dela- Ware Filed May 5, 1958, Ser. No. 732,944 5 Claims. (Cl. 18-8) The present invention relates generally to the production of artificial yam by the melt-spinning process and more particularly to a system for controlling the leakage around pumps used to convey molten polymeric material from a supply reservoir to a spinning plate for extrusion.

In the grid or melt-spinning of artificial yarn, polymeric chips are fed from a bunker or chip column to a heated grid where the material melts and gravitates to a supply reservoir. The molten viscous material passes from the reservoir to a first or pressure pump, after which it is forced under pressure to a second pump. This second pump meters out a predetermined amount of the molten polymer supplied thereto and feeds the same to a spinneret having a suitable opening or orifice therein for forming yarn from the polymer extruded therethrough. The freshly-extruded yarn passes from the spinneret into a cooling zone, after which the same solidifies and may be collected in package form. This overall process is well known and in itself forms no part of the present invention. It is in the use of this process, however, that the problems to which this invention relates originate.

As previously mentioned, the pumps used in the manner described herein operate under pressure which is necessary in order for the extrusion function to be performed. An inherent dis-advantage concomitant with use of these pumps is leakage of the material being pumped along the drive shaft to the outside of the pump housing, which leakage eventually passes along the outer surface of the spinning assembly into the spinning column therebelow and impairs the spinning operation.

The industry has long been concerned with pump leakage, and many attempts have been made to prevent the same. For example, it has been proposed in US. Patent No. 2,412,588 that the liquid pumped be recirculated from the ends of the drive shaft back into the inlet side of the pump. In this manner, the pumped liquid may serve as a shaft lubricant and yet the same will not migrate to the outside and build up on the pump housing. This system is not satisfactory for the pumping of polymeric material, however, since the recirculated lubricating material has been found to contaminate the spinning solution and produce an inferior quality product. Various seals alsohave been proposed, but to the best of applicants knowledge, none of these attempts to prevent pump leakage have been commercially successful.

. An object of 1 the present invention is to provide a process and apparatus for overcoming the aforesaid disadvantages of known spinning pumps.

Another object of this invention is to provide a spinning system which will eliminate the necessity for periodic maintenance due to spinning pump leakage.

A further object of the present invention is to provide a process and apparatus for controlling the direction of leakage along the drive shaft of pumps used in the spinning of polymeric or othertype materials.

Still anotherobject of this invention is to provide a process and apparatus capable of isolating inherent leakage of spinning-pumps from the main body of spinning An additional object oi -the present invention is to provide a process and apparatus for collecting inherent "ice leakage of spinning pumps at a point remote pump housing.

Another object of this invention is to provide an apparatus for collecting pump leakage indefinitely Without discontinuing operation of the pump.

A further object of the present inventionis to provide a removable leakage collecting container which can be removed readily tfrom operative position and emptied or replaced in a matter of seconds.

Still another object of this invention is to provide a system for controlling the leakage of spinning pumps to which conversion is easily accomplished and for which maintenance is economical.

A still additional object of the present invention is to provide a system for controlling the leakage of spinning pumps which requires no substantial change in existing equipment and very few additional elements.

Other objects and advantages will become apparent hereinbelow.

The present disclosure, as indicated above, relates not to the prevention of pump leakage but to a system for controlling the direction of leakage along the pump drive shaft, for isolating this leakage from the solution being pumped, and for collecting the leakage at a point remote from the pumps.

Conventional gear-type spinning pumps (hereinafter used to designate both the pressure and the metering pumps) generally used in the grid-spinning of polymeric material are supplied by'the manufacturer with a longitudinal bore through the center of the pump drive shaft, this bore being provided for the purpose of equalizing axial thrust due to pressure build-up on opposite ends thereof. The spinning system disclosed herein utilizes this bore for an entirely dilierent purpose, but does not destroy or affect in any way the original function.

The objects of this invention may be accomplished by providing leakage ports in the spinning blocks on which the spinning pumps are mounted, which ports extend from the innermost end of the longitudinally bored pump drive shafts, where they are aligned with the aforesaid bore, to and through a spinning plate positioned beneath the spinning blocks. Pump leakage is forced by the high pressure action of the pump, from the pumping zone of the pump gears along the drive shaft toward the ends thereof, with that portion of the leakage along the drive or outermost end of the shaft being diverted into and entering and passing through the longitudinal bore to the leakage ports, and that portion of the leakage at the innermost end being diverteddirectly into these ports, after which the combined leakage is forced by the action of additional leakage through the spinning blocks and spinning plate into a suitable container positioned therebelow. The container may be removed, emptied and/or replaced periodically.

A detailed description of one embodiment of this infrom the vention will now be given with attention directed to the accompanying drawings, wherein:

FIGURE 1 is an. elevational view, partly in section, of one melt-spinning position embodying the leakage control concept mentioned above; and

,FIGURE 2 is a perspective view of a leakage collec tion tray suitable forfuse with the apparatus of FIG- URELI" The single melt-spinning position indicated generally by reference numeral 10 in FIGURE 1 comprises a melting grid I1, an upper spinning block 12, a lower spinning block 13, a spinning plate 14, and a spinning column or blowbox 15 which is separated from the spinning plate by insulation material or insulator 16. All of these elements are positioned one with respect to the other in the manner shown by the drawings, and are bolted together by means not shown.

Polymer chips are fed from the bunker or chip column 17 (only partially shown) into heated grid 11 where they are melted and passed down into the polymer reservoir 18. All of the polymer passageways leading from this reservoir to the spinning plate are indicated by dotted lines. As can be seen in FIGURE 1, a suitable passageway 20 interconnects the reservoir 18 with the inlet conduit of gear-type pressure pump 21; passageway 22 leads from the outlet conduit of pressure pump 21 to the inlet conduit of gear-type metering pump 23; and passageway 24 leads from the outlet conduit of the last-named pump into the spinning chamber of spinning plate 14, where the molten material is extruded through apertured spinneret 25 into the blowbox 15, from which the freshly extruded yarn is fed to a suitable take-up.

Main drive shafts 26, 27 impart rotation to pump drive shafts 28, 30, respectively, as well as to'the gears splined thereto, through the couplings shown, as indicated by the arrows. These couplings are rotatably supported within stationary hubs 29 which are bolted to the respective pump housings. Shafts 31, 32 generally are non-rotatively mounted within the housing of pumps 21, 23, respectively, and rotatably support the driven gears in each instance. For purposes of this application, and as shown in the drawings, pressure pump 21 and metering pump 23 may be substantially identical. Each comprises a front plate 33 through which inlet and outlet conduits pass and in which are journaled one end of each of the two pump shafts shown, a central plate 34 suitably bored to receive the pump gears, and a back plate 35 apertured to receive the opposite ends of the two shafts. The interengaging faces of these plates are precision machined 1n order to seal off the gears when the pumps are bolted to the respective spinning blocks. All of the structure discussed up to this point is of conventional design and, except to the extent that it contributes to the overall combination claimed herein, forms no part of the present inventive concept. i A large majority of the leakage previously encountered in the melt-spinning of polymeric material, with gear-type spinning pumps such as here shown, occu-rsaround the pump drive shafts 28, 30 from which it flows out between the drive couplings and hubs, and covers the outer surfaces of the pump housings. Subsequent leakage builds up, flows down over the spinning blocks and eventually covers the spinning plate, blowbox, etc. When this happens, it becomes necessary to replace the melting grid and to clean the entire spinning assembly, which operation requires a considerable amount of time and labor, notto mention the loss in production wihle the machine is undergoing repair. V

I The entire length of the pump drive shafts 28, 30 are pre-drilled with longitudinal bores 36, 37, respectively, for a purpose mentioned earlier. Molten polymer flows into each of these bores in conventional spinning assemblies, but since the innermost end of each shaft 'is' fitted against a solid surface of the adjacent s'pinning'block,

the leakage can migrate only to the outermost end of the bores, from which it passes between the drive couplings and hubs outside of the pump housings. The present system provides a leakage pathhavingless resistance to flow than the normal'path just described, as will now be explained.

A first substantially horizontal leakage port 38 is drilled or otherwise formed in spinning block 12. The

exposed or outer end of this port is aligned, with the innermost end of longitudinal bore 36 .in pump drive shaft 28, as shown. A first substantially'vertical leakage port 40 also is formed in spinning block 12, this port connect- ;ing with the innermost endv ofport 38 and leading to the One or more of these cavities are provided in most spinning plates for the purpose of reducing weight of the same. A second substantially horizontal port 43 is formed in spinning block 13 in such a manner as to extend between the innermost end of longitudinal bore 37 and the second vertical port 41. These ports are slightly larger than the longitudinal bores mentioned, so as to offer very little resistance to polymer'flow, may be formed by drilling or any other suitable means.

The system described above has been found to operate satisfactorily where the quantity of leakage is relatively low. In other words, the capacity of lightening cavity 42 is sufiicient, in some instances, to store leakage polymer until such time as the spinning position must be disassembled for reasons other than leakage'maintenance,

be greatly expedited.

The overall spinning process was improved by the leakage control system disclosed herein to such an extent, however, that the regularly scheduled maintenance periods became less frequent in occurrence. It was desired, therefore, to provide a leakage collection apparatus that would store a larger capacity of polymer, preferably one which would store leakage indefinitely so that the operative period of the spinning assembly would not be limited thereby. A collection device satisfying these conditions will now be described with reference first to FIGUREl and subsequently to FIGURE 2;

An outlet port 44 is formed in that normally closed or solid portion of spinning plate 14 which defines the bottom of cavity 42. This permits leakage polymer to flow from the'spinning pumps 21, 23 through the spinning blocks 12, 13, spinning plate 14, and into the space therebelow, which is surrounded by generally circular insulator 16 and the blowbox 15. A leakage collection tray 45 is slidably positioned within a suitable elongated opening 46 which is formed in the insulator 16 and which extends transversely of the spinning plate 14. For a more detailed description of this tray, attention is directed to FIGURE 2.

The tray 45 comprises an elongated main vcollection trough 47 and a box-like storage compartment 48 formed integral therewith and having greater depth and capacity than the trough. A tray rake 50 is movably mounted within the trough 47 and may be operated through guide rods 51 secured thereto and extending longitudinally along the tray adjacent and parallel to the .side walls 52, 53.

These rods are slidably supported by suitable apertures the accumulated leakage polymer may be conveyed into the storage compartment bymanipulation of handle 55 and rake 50, which readies the tray for subsequent collection. Upon filling of the trough and storage compartment,

the tray may be removed by pulling the same outwardly from the opening. 46 in insulator 16, after which-it may be dumped or replaced with an empty tray of comparable size. Although leakage polymeris fed to the tray through only one lightening cavity 42 in the embodiment shown,

' it -is of course possible to utilize more than one of these Tcavities by proper disposition of the tray thereunder, and by the provisioin of, suitable additional leakage ports therethroughf The leakage polymer collected in trough 47 is not sufficiently molten to spread; consequently, means such as rake 50 must be provided in order to utilize the additional capacity of storage compartment 48. A trough portion of the same depth as the storage compartment, although desirable, is not possible unless the blowbox be altered considerably. On the other hand, the insulator may be easily modified by cutting or otherwise forming the elongated opening 46 sufiiciently larger than the tray so that sliding movement'of the latter will be facilitated. It has been found that removal of this portion of the insulatordoes not affect operation thereof deleteriously.

' The path of flow of the controlled leakage concept under consideration will next be explained in connection with pump 21. As can be seen in FIGURE 1, the inlet and outlet conduits of this pump lead from the spinning block 12 through front plate 33 to the zone of intermeshing The quality of yarn produced by the present system has been found to beat least as high as that produced with conventional assemblies. As a matter of particular interest, the fleck count, which may be defined as the number of irregular enlarged sections in a given amount of yarn, was very low, which was completely unexpected. For example, yarn produced in accordance with known systems contained 11.74 flecks per pound, whereas yarn produced on an adjacent machine modified in accordance with this invention contained only 1.00 fleck per pound.' Although there is no immediate explanation, this result is highly desirable. I

The following chart indicates that other properties of the yarn were substantially the same as had been obtained before, the first line representing yarn produced on a modified machine and the second pertaining to yarn produced on a conventional assembly.

After Drawtwlstlng Strength Elongation Evenness Denier (gms./10OD) (percent) (Zellweger) Percent Percent Standard Discarded between the gears carried on the drive shaft 28 and stationary shaft 31. As mentioned previously, there is very little tendency for leakage to occur around the stationary shaft since there is no relative motion between it and the pump housing. Polymer contained under pressure within the intermeshing zone, however, migrates upwardly along the end faces of the drive gear to the outer surface of the rotatable drive shaft, and along this shaft to the respective ends thereof, all as shown by arrows. Polymers passing to the innermost ends of course enters the leakage port 38 immediately. Polymer passing to the outermost end of the drive shaft, however, must be diverted into the longitudinal bore 36. This diversion is accomplished by virtue 'of the greater resistance to flow otfered by the coupling and hub overlying this end of the shaft than by the leakage port 38. This p'ort'ionof leakage, consequently, passes into and through the bore 36 and eventually emerges at the entrance to port 38.

The leakage of additional polymer around the gears forces the first portion along the port 38, into the port 40 and finally through the cavity 42 into the tray 45, this action continuing without interruption so long as the pump 21 is in operation. The leakage within pump 23, also shown by arrows, travels in substantially the same manner as explained above, but of course passes into horizontal port 43 rather than port 48. The entire spinning assembly is maintained at an elevated temperature, as mentioned earlier, which prevents complete solidification of the polymer prior to collection in tray 45.

Operation of the leakage control concept described hereinabove has proceeded with much success. Test units have been run for as long as 33 days without change in the spinning pumps. Upon inspection, these pumps were found to be completely free of polymer leakage. As a matter of fact, they were as clean as when originally installed. In contrast to this, it was heretofore necessary to clean or replace these same pumps on an average of every days if the leakage were allowed to flow uncontrolled outside the pump housing.

In one experiment, only the lower spinning block was modified, and the assembly was operated for 19 days. When the grid was removed, the metering pump attached to the modified block was found to be clean, with absolutely no leakage to the outside. On the contrary, however, the pressure pump attached to the unmodified block had leaked sufficiently to cover the outer pump surface. Additionally, no leakage polymer has been found inside the melting grid housing after use of the novel system herein described.

The leakage collection tray shown in FIGURE 2 normally' operates for about 48 hours before emptying is required. It is generally necessary, however, to rake leakage polymer from the trough into the storage compartment approximately every six hours. It is again pointed out, however, that neither operation requires interruption of the spinning process.

It is felt that utilization of the present leakage control concept will reduce the number of required grid changes by at least 25 percent. With a sliding grid of the type disclosed in U.S. application Serial No. 691,416, filed October 21, 1957, and owned in common herewith, it is possible that a spinning assembly could be operated indefinitely without shut downs due to the necessity for cleaning. The down time required for changing a sliding grid is much less than that required in the change over of conventional grids, as explained in the aforesaid copending application, with the overall result being that the total down time of any given assembly for maintenance purposes would be greatly reduced. At any rate, the operating cycle of a spinning assembly modified as suggested herein is limited only by the useful life of the melting grid, as distinguished from the shorter useful life of the spinning pumps when spinning according to conventional practice.

While only one specific embodiment has been shown herein, it is expected that other modifications will become apparent to those skilled in this art upon study of the instant disclosure. Accordingly, it is intended that the scope of this invention be limited only to the extent set forth in the attached claims.

What is claimed is:

1. A leakage control process for use in the melt spinning of polymeric material utilizing a spinning pump having a longitudinally bored, rotatable, drive shaft, comprising the steps of supplying molten polymeric material to said pump, pumping said material through an outlet of said pump to an extrusion zone and thereby accumulating polymer leakage around said drive shaft, diverting at least a portion of said leakage through said longitudinal bore to a point within the spinning assembly but isolated from the supply and outlet of said pump, and collecting the diverted leakage without disturbing the spinning operation and while maintaining the same isolated from the molten polymeric material passing to said extrusion zone.

2. A melt spinning system comprising a spinning block, a gear-type spinning pump secured to said spinning block and having a longitudinally bored, rotatable, drive shaft,

means for supplying polymeric spinn ng material to said pump, means for receiving said spinning material from said pump and for extruding the same into yarn, means defining a leakage control port within said spinning block extending from one end of said drive shaft'and interconnecting said longitudinal bore with a point isolated from said spinning pump, means for diverting melt leakage from along said shaft into said longitudinal bore, and removable means for collecting leakage diverted'through said longitudinal bore and said leakage control port while maintaining said diverted leakage isolated from the spinning material supplied to said pump.

3. In a melt spinning system having a spinning block, a spinning plate secured to one surface of said spinning block, a spinning pump secured to another surface of said spinning block, said spinning pump having a longitudinally bored, rotatable, drive shaft, means for supplying molten polymeric material to said spinning pump, and means supported by said spinning plate for receiving said material from said pump and for extruding the same into yarn, the improvement comprising means defining a leakage control port within said spinning block isolated from and extending from one end of said longitudinally bored drive shaft to and through said spinning plate, means for diverting melt leakage from along said shaft into said longitudinal bore, and means for collecting leakage diverted through said port while maintaining the same isolated from the molten polymeric material supplied to said pump.

4. In a melt spinning system having a spinning block, a spinning plate secured to one surface of said spinning block, a pressure pump secured to another surface of said spinning block, at least one metering pump secured to still another surface of said spinning block, each'of said pumps having a longitudinally bored, rotatable, drive shaft, means for supplying molten polymeric material to said pressure pump, conduit means connecting said pressure pump with said metering pump whereby the outlet from the former will be fed to the latter, and means supported by said spinning plate for receiving material from the metering pump and for extruding the same into yarn, the improvement comprising means defining a substantially horizontal leakage control port extending fiom the bored shaft of each pump to a point within said spinning block isolated from said supply and extruding means, 'means for diverting melt leakage from along the pump shafts into the longitudinal bores thereof and to the horizontal leakage control port corresponding therewith, means defining a substantially vertical leakage port within said spinning block communicating with said horizontal ports and extending to and through said spinning plate, and a leakage collection tray removably supported beneath said spinning plate for collecting leakage polymeric material diverted through said leakage ports while maintaining the same isolated from said supply and extruding means.

5. Leakage control means for use in the melt spinning of polymeric material utilizing a spinning pump having a longitudinally bored, rotatable, drive shaft, comprising means for supplying molten polymeric material to said pump, means for pumping said material through an outlet of said pump, thereby accumulating polymer leakage around said drive shaft, and for extruding the material into yarn, means for diverting said leakage through said longitudinal bore to a point within the spinning assembly but isolated from the supply and outlet of said pump, and means for collecting the diverted leakage without disturbing the spinning operation and while maintaining the same isolated from said supply of molten polymeric material and from said extruded yarn.

References Cited in the file of this patent UNITED STATES PATENTS 2,252,684 Babcock Aug. 19, 1941 2,278,875 Graves Apr. 7, 1942 2,369,506 Weibe Feb. 13, 1945 2,420,622 Roth et a1. May 13, 1947 2,432,576 Kotfer Dec. 16, 1947 2,571,377 Olah Oct. 16, 1951 2,715,753 McLellan Aug. 23, 1955 2,781,730 Newmier Feb. 19, 1957 2,791,374 Lingg May 7, 1957 2,792,171 Rosset May 14, 1957 

